Electrostatic control method and apparatus

ABSTRACT

An electrostatic control method and apparatus wherein a potential difference is impressed across two or more electrically conductive members which are electrically isolated from one another to provide the adjacent members with opposite electrical polarity and thereby create an electrostatic force urging the members together against the resistance of an opposing resilient force. The potential difference is adjusted to effect relative positioning of the members through a range of positions under the conjoint action of the electrostatic force and the opposing force. The disclosed inventive embodiment is a thermal barrier composed of multiple thermal insulating layers which are electrostatically positioned to regulate the thermal conductance of the barrier.

United States Patent [191 Clifford 1 1 ELECTROSTATIC CONTROL METHOD ANDAPPARATUS [75] Inventor: Richard P. Clifford, Newport Beach, Calif.

[73] Assignee: TRW Inc., Redondo Beach, Calif. [22] Filed: Jan. 2, 1973[21] Appl. No.: 320,143

Related US. Application Data [62] Division of Ser. No. 214,900, Jan. 3,1972.

[111 3,816,772 June 11, 1974 Primary Examiner-J. D. Miller AssistantExaminer-Harry E. Moose, Jr.

Attorney, Agent, or FirmDaniel T. Anderson; Donald R. Nyhagen; Jerry A.Dinardo [57] ABSTRACT An electrostatic control method and apparatuswherein a potential difference is impressed across two or moreelectrically conductive members which are electrically isolated from oneanother to provide the adjacent members with opposite electricalpolarity and thereby create an electrostatic force urging the memberstogether against the resistance of an opposing resilient force. Thepotential difference is adjusted to effect relative positioning of themembers through a range of positions under the conjoint action of theelectrostatic force and the opposing force. The disclosed inventiveembodiment is a thermal barrier composed of multiple thermal insulatinglayers which are electrostatically positioned to regulate the thermalconductance of the barrier.

4 Claims, 1 Drawing Figure PATENTEDJUMI m4 33 7 Temp SensorELECTROSTATIC CONTROL METHOD AND APPARATUS This is .a division, ofapplication Ser. No. 214,900, filed Jan. 3, 1972.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates generally to the field of electrostatic and more particularly toa novel electrostatic control method and apparatus for electrostaticallypositioning electrically conductive members relative to one another.

2. Prior Art Electrostatically controlled relays are known in the art.These relays have a movable contact which is positionedelectrostatically rather than electromagnetically as in a conventionalelectromagnetic relay. Thus, in an electrostatic relay, the movablecontact is retained in a normal position by spring action and is movableto a second position by electrostatic force. This force is created byimpressing across the contact and a part of the relay toward which thecontact moves to its second position a potential difference whichcharges the contact and part to opposite electrical polarity. Thecontact is returned to normal position by spring action by shortcircuiting the contact and part to remove their opposite charges.

Such relays are essentially two position devices wherein theelectrostatically positioned element, i.e., the movable contact, hasonly two possible positions. Examples of these relays are found in US.Pat. Nos.:

SUMMARY OF THE INVENTION The present invention provides an electrostaticcontrol method and apparatus for electrostatically positioning two ormore electrically conductive members through a range of positions and/orpositioning two or more members in response to a selected monitoredparameter. To this end, the electrostatic control apparatus has two ormore electrically conductive members which are spaced along and movablerelative to one another along a given direction line. The members areurged apart by spring action. Means are provided for impressing apotentialdifference between the members such that the adjacent membersare charged to opposite electrical polarity so as to create anelectrostatic force which urges the members together against theopposing springforce. The potential difference is variable to vary theelectrostatic force and thereby position the members relative to oneanother through a range of positions under the conjoint action of theelectrostatic force and the opposing. spring force.

The disclosed inventive embodiment is a thermal barrier wherein theelectrostatically positioned members are sheets of crumpled thermalinsulation, such as crumpled. plasticfilm with a metallized coating onone surface. Thesev sheets are disposed in contacting faceto-facerelation, such. that the adjacent sheets contact one another only at alimited number of local contact points provided by the crumpled orwrinkles in the films. The contacting wrinkles act as springs of a sortwhich yieldably urge the insulating sheets apart.

A d-c charging circuit is provided having a positive thermal connectedto the metallized coating of alternate sheets and a negative thermalconnected to the metallized coating of the intervening sheets. Thischarging circuit creates between the sheets a potential difference whichelectrically charges the adjacent sheets to opposite electrical polarityto create an electrostatic force for urging the sheets together.Included in the charging circuit are means for regulating the potentialdifference to effect relative positioning of the insulating sheets forthe purpose of controlling or regulating the thermal conductance of thethermal barrier. Thus increasing the potential difference compresses orcompacts the sheets, i.e., urges the sheets into more intimate contact,to increase the thermal conductance of the barrier. Reducing or removingthe potential difference permits the sheets to spring apart to reducethe thermal conductance of the barrier.

The disclosed thermal barrier is used to automatically control orregulate thermal energy transfer between two thermal regions located atopposite sides of the barrier for purpose of regulating the temperaturein one region. To this end, the charging circuit for for the barrier isequipped with means for sensing the temperature in the regulated regionand controlling the potential difference impressed on and thereby thethermal conductance of the barrier in response to changes in the sensedtemperature. A primary application of the invention, for example,involves use of the thermal barrier as a thermal radiator on aspacecraft to effect automatic control of the temperature in thespacecraft. In this application, the thermal conductance of the thermalbarrier is regulated to regulate heat rejection from the spacecraft toambient space in response to the temperature within the spacecraft.

The invention is also capable of other applications. For example, theinvention may be utilized to provide an electrostatically controlledvariable capacitor wherein the electrostatically positioned members arethe capacitor plates.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawingillustrates an automatic electrostatic temperature control systemaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated electrostaticcontrol system 10 has a number of electrically conductive members l2, l4disposed side-by-side along a common axis 16 and movable toward and awayfrom one another along the axis. Members 12, 14 are electricallyisolated from one another and are urged apart by a spring force whichnormally retains the members in relatively separated positions. Anelectrical charging circuit 18 is connected to the members forimpressing on the members a potential difference which electricallycharges the adjacent members to opposite electrical polarity. Anelectrostatic attractive force is thereby created on the members whichurges the members together. Included in the charging circuit are means20 for regulating the potential difference to effect relativepositioning of the members along the axis 16 under the conjoint actionof the electrostatic force and opposing spring force.

The particular electrostatic control system illustrated is a temperaturecontrol system for regulating thermal energy transfer between twothermal regions 22 and 24. In this application, the electrostaticallypositioned members l2, 14 provide a thermal barrier 26 which is locatedbetween the thermal regions and whose thermal conductance iselectrostatically regulated to regulate thermal energy transfer betweenthe regionsand thereby the temperature in one region. For example, inthis disclosure, thermal region 22 is assumed to be the interior of aspacecraft and thermal region 24 is assumed to be ambient space. Thermalbarri'er 26 provides a thermal radiator which absorbs heat from'thespacecraft interior 22 and radiates the heat to space 24.

Referring in more detail to the thermal control system illustrated, theelectrostatically positioned members 12 of the thermal barrier 26comprise sheets or layers of thermal insulation, such as crumpledplastic films with a metallized coating on one surface. These layers aredisposed in contacting face-to-face relation along the axis 16. Member14 of the thermal barrier is an external radiator in the form of a metalplate or the like. It is important to note here that the barrier layersl2, 14 have been shown as spaced for the sake of clarity. In actualpractice, however, the layers will contact one another at local contactpoints provided by the crumples or wrinkles in the layer sheets. Thesecontacting wrinkles provide springs of a sort which exert on the layersspring forces for urging the layers apart. The inner surface of theinnermost layer 12 is blackened to provide an efficient thermalabsorption surface. Thermal energy transfer from the region 22 to theregion 24 occurs by radiation to the innermost barrier layer 12, then byconduction and radiation through the layers l2, l4, and finally byradiation from the outermost layer 14.

Charging circuit 18 has a high voltage d-c power supply 28 and a voltageregulating switch 30. Power supply 28 has a negative terminal 32 and anumber of positive terminals 34 at different voltage levels. Negativeterminal 32 is connected to a stationary contact 36 of a switch andtothe metallized coating of alternate layers of the thermal barrier 26including the outer layer or radiator plate 14. The positive terminals34 of the power supply are connected to stationary contacts 38 of switch30. Switch 30 has a movable contact connected to the metallized coatingof the remaining intervening layers of the thermal'barrier 26 through acurrent limiting resistor 42. The adjacent barrier layers areelectrically isolated from one another, as by arranging the layers 12with their metallized coatings facing away from radiator 14, such thatthe adjacent layers are insulated from one another by their plasticfilms.

From the description thus far, it is evident that movement of themovable contact 40 to any one of the switch contacts 38 impresses on thethermal barrier layers 12, 14 a potential difference which electricallycharges the adjacent layers to opposite polarity. This potentialdifference creates an electrostatic force on thebarrier layers whichurges the layers together, i.e., compacts or compresses the layers,against the action of the spring force which urges the layers apart. Thelayers are thus effectively positioned relative to one another by theconjoint action of the electrostatic force and opposing spring force onthe layers. Compression of the barrier layers in this way provides moretotal contact surface area between the adjacent layers and therebyincreases the thermal conductance of the barrier. Since theelectrostatic compression force and hence thermal conductance increaseswith the potential difference impressed between the layers, the thermalconductance of the thermal barrier may be regulated or varied by movingthe switch contact 40 from one stationary contact 38 to another.

The thermal conductance of the thermal barrier 26 is reduced to aminimum by moving the switch contact 40 to stationary contact 36. Theseveral thermal barrier layers l2, 14 are thereby short circuitedthrough the current limiting resistor 42 to remove or dissipate theelectrical charges on the layers. The layers then separate under springaction to their normal minimum conductance positions. The voltagesimpressed on the thermal barrier layers l2, 14 will vary from oneapplication to another depending on factors such as the material of thelayers, their size and thickness, and other factors. A typical meanvoltage level, however, may be on the order of 300 Vdc.

In the particular embodiment shown, the switch 30 is actuatedautomatically in response to the temperature in region 22 to maintainthis temperature relatively constant. To this end, the movable switchcontact 40 is connected to a driver 44 controlled by a temperaturesensor 46 within the region 22. Driver 44 positions the switch contact40 in response to temperature changes in the region 22 in such a waythat increasing temperature effects movement of the contact to increasethe voltage applied to and thereby the thermal conductance of thethermal barrier and thereby increaseheat rejection through the-barrierto the outer space region 24. A decrease in the temperature within theregion 22 has the opposite effect.

In the particular electrostatically controlled thermal barrierillustrated, the outer radiator layer 14 may form an integral part ofthe barrier or it may be the outer skin of the spacecraft. A thermalbarrier according to the invention may also be formed by applying asingle electrostatically controlled layer about a metallic object to bethermally controlled. In this case, the wall of the object forms thesecond layer of the thermal barrier.

What is claimed as new in support of Letters Patent l. Electrostaticapparatus comprising:

a stack of at least two resiliently flexible, electrically conductivelayers electrically isolated from one another and disposed side-by-sidewith spaced portions of adjacent layers normally disposed in seatingcontact for resilient deflection of the intervening portions betweensaid contacting portions toward and away from one another and resultantcompression and expansion of said layer stack;

means for impressing a potential difference between said layers in amanner such that the adjacent layers are electrically charged toopposite electrical polarity to create an electrostatic attractive forceproportional to said potential difference between said layers fordeflecting said intervening layer portions toward one another andthereby compressing said layer stack; and

means for regulating said potential difference to vary said force.

2. An electrostatic apparatus according to claim 1 wherein:

said layers comprise crinkled plastic film having corresponding metalliccoated surfaces. 3. The electrostatic method which comprises the stepsof:

wherein:

trically charged to opposite electrical polarity, whereby said potentialdifference produces an electrostatic attractive force proportional tosaid potential difference between said layers for deflecting saidintervening layer portions toward one another and thereby compressingsaid layer stack; and

regulating said potential difference to vary said force.

4. The electrostatic method according to claim 3 said layers comprisecrinkled plastic film having corresponding metallic coated surfaces.

1. Electrostatic apparatus comprising: a stack of at least tworesiliently flexible, electrically conductive layers electricallyisolated from one another and disposed side-by-side with spaced portionsof adjacent layers normally disposed in seating contact for resilientdeflection of the intervening portions between said contacting portionstoward and away from one another and resultant compression and expansionof said layer stack; means for impressing a potential difference betweensaid layers in a manner such that the adjacent layers are electricallycharged to opposite electrical polarity to create an electrostaticattractive force proportional to said potential difference between saidlayers for deflecting said intervening layer portions toward one anotherand thereby compressing said layer stack; and means for regulating saidpotential difference to vary said force.
 2. An electrostatic apparatusaccording to claim 1 wherein: said layers comprise crinkled plastic filmhaving corresponding metallic coated surfaces.
 3. The electrostaticmethod which comprises the steps of: selecting a stack of at least tworesiliently flexible electrically conductive layers which areelectrically isolated from one another and arranged side by side withspaced portions of adjacent layers normally disposed in seating contactfor resilient deflection of the intervening portions between saidcontacting portions toward and away from one another and resultantcompression and expansion of said layer stack; impressing a potentialdifference between said layers in a manner such that the adjacent layersare electrically charged to opposite electrical polarity, whereby saidpotential difference produces an electrostatic attractive forceproportional to said potential difference between said layers fordeflecting said intervening layer portions toward one another andthereby compressing said layer stack; and regulating said potentialdifference to vary said force.
 4. The electrostatic method according toclaim 3 wherein: said layers comprise crinkled plastic film havingcorresponding metallic coated surfaces.